High formation pressure is the most critical problem hindering formation of gas hydrates in industrial scale for storage and transportation of natural gas. The effects of tetrahydrofuran (THF) and tetrahydropyran (THP) on the phase equilibrium of methane hydrate have been studied. The addition of THF at different concentrations of 1, 2.5 and 6 mol % and THP at 6 mol % aqueous solutions caused hydrate equilibrium pressure to drastically reduce at a specified temperature. While the equilibrium pressure of methane hydrate is about 34 MPa at 293K, this equilibrium pressure decreased to about 2.5 MPa using 2.5 mol % of THF. Furthermore, the hydrate equilibrium temperature greatly increased at a specified pressure. The equilibrium temperature of methane hydrate at 5 MPa is about 278K. This equilibrium temperature increased to about 306K using 6 mol % of THF.